Tubular glass containers such as ampoules, phials and the like



July 28, 1959 s, s w I 2,896,807

TUBULAR GLASS CONTAINERS SUCH AS AMPOULES, PHIALS AND THE LIKE FiledFeb. 19. 1954 fnumtor 650M574 NLE y 6/171 w Attorneys United StatesPatent TUBULAR GLASS CONTAINERS SUCH AS AM- POULES, PHIALS AND THE LIKEGeorge Stanley Shaw, Liverpool, England, assignor to Glass Containers(Medical) Limited, Liverpool, England Application February 19, 1954,Serial No. 411,453 5 Claims. (Cl. 215-32) This invention relates totubular glass containers of the kind known as ampuls, which are formedwith a reduced or tapered end at which they are sealed after filling andare formed with a constriction or neck where the reduced end joins themain body of the ampul and at which constriction the ampul is usuallybroken to gain access to the contents. More particularly, the presentinvention has to do with a constrictive type of ampul so constructed asto be easily breakable when properly grasped but at the same timeprovide an ampul highly resistant to accidental breakage.

The recognized problem in the ampul art has been the provision of anampul which may be conveniently broken by the consumer and one whichwill withstand accidental breakage during filling, shipping, orhandling. For example, the patent to Thomae No. 1,951,743 provides ascratched point in the neck of the ampul and claims protection againstaccidental breakage by the use of an adhering outer coating. An exampleof providing ampuls to be conveniently broken by the consumer is setforth in the patent to Smith No. 2,517,604 wherein a portion of theampul is placed under a stress of tension by the fusing of material tothe exterior surface of the ampul to weaken the fragibility of the glassat such point. An example of other attempts to reinforce the ampulagainst accidental breakage is set forth in the patent to OSullivan No.2,486,321 wherein a constrictive type of ampul is reinforced at theconstricted area by spaced ridges but still permitting the ampul to bebroken by subsequent application of a scoring or scratching implementsuch as a file.

The present invention envisages the creation of a locality at which thestrength of the glass changes so as to determine the locality of thebreak. The invention further envisages the proportioning of the wallthickness with respect to the diameter of the constriction and/orcontrolling the quality of the glass at such proportioned wall thicknessto thereby provide great resistance to premature or accidental breakingof the ampul but still providing an ampul to give a clean successfulbreak.

Another feature of the present invention consists of manufacturing anampul with a scratch or notch formed in the external surface thereof atthe constriction and in annealing the ampul after the formation of thescratch or notch.

Another feature of the present invention has to do with theproportioning of the wall thickness of the ampul at the constriction sothat it is not less than 8% of the outside diameter at the constrictedneck, the maintenance of the wall thickness, as well as the annealingafter the forming of the breakage scratch or notch, both contributing tothe strength of the ampul against accidental breakage withoutunnecessarily contributing against purposeful breakage.

A further feature of the invention consists in limiting the depth andannular length of the scoring, etching or other breaking effect appliedto the external surface of ice the ampul at the constriction butrelative to the wall thickness at such point of application to furtherinsure against inadvertent breaking of the ampul during cleaning,filling or other handling operations.

Other objects and advantages of the invention will be readily apparentfrom the following description and accompanying drawings wherein Figurel is an elevation of a constricted type ampul showing the notch formedat the apex of the constriction.

Figure 2 is an enlarged fragmentary section taken on the line II-II ofFigure 1.

Figure 3 is an enlarged fragmentary horizontal sectional view taken onthe line III-III of Figure 2.

The ampul shown in Figure 1 has a constricted neck 1 between the mainbody portion 2 and a tapered end portion 3 which is open at its upperend. The contents are fed into the ampul through the upper end which issubsequently hermetically sealed with the aid of heat.

As shown in Figure 2 the wall 4 of the constricted neck 1 is ofthickness between 10% and 15% of the external diameter of the neck andhas a short notch 5 scored therein at the narrowest part of the neck topreweaken it.

The formation of the neck or constriction .1 in an ampul obviouslydefines the general point of breakage and the addition of a preweakeningzone such as by scoring or otherwise placing a portion of theconstriction under stress obviously amplifies weakening of the ampulwith respect to inadvertent breakage. It is a primary object of thisinvention to provide a simple, inexpensive ampul of the neck orconstricted type which will withstand an unusual amount of shock andvibration to prevent inadvertent breakage, without the application ofany external protective means, and which will at the same time be highlyefficacious as to clean purposeful breakage.

As one contributing factor to accomplish this resistance to inadvertentbreakage, I have found that in an ampul of the necked or constrictedtype the ratio between the wall thickness at the constriction 1 and thediameter of the constriction is important, and should not be less than agiven value.

Thus the present invention comprises a method of manufacturing glassampuls of the kind above set forth in which in the case of ampuls madeof neutral glass the ratio of the thickness of the ampul wall at theneck to the outside diameter of the neck is maintained at not less than8% and in the case of ampuls made of glass of more or less inherentstrength or resistance to breakage than netural glass the said ratio ismaintained at not less than 7% or 9% respectively and in which the ampulis preweakened at the neck, preferably by transversely scoring the neck,to an extent only suflicient to facilitate intentional breakage of theampul at the neck by the application of a bending moment thereto.

When the ampuls are preweakened by scoring it is preferable that thescoring should be carried out prior to annealing, that is to say thenormal annealing operation will be carried out after scoring.

In general it is to be preferred that the thickness of the glass wall atthe neck should be maintained at not less than 10% and not greater than15% of the external diameter of the neck and this is particularly so inthe case of small ampuls with necks of the order of 4 millimetres to 6millimetres in external diameter. It is desirable in the case of smallampuls having a relatively small diameter at the neck that the thicknessof the wall at the neck should be maintained Well above the lower limitof 8% even though satisfactory results can be achieved with wallthicknesses as low as 8% of the neck diameter.

Maintenance of the wall thickness at the neck at not less than 8% andpreferably at not less than 10% and 3. not more than 15% of the externaldiameter of the neck is very important because it is this which rendersthe ampuls sufficiently robust at the neck to enable them to bepreweakened to an extent sufiicient to facilitate intentional breakagethereof by the consumer without undue risk or inadvertent breakageduring subsequent cleaning, filling and transit thereof. If the wallthickness is not maintained as set forth above the result may be thatsome ampuls of a batch when preweakened may have sufficient strength atthe neck to withstand the normal hazards of cleaning, filling andtransit whilst others will be of insufficient strength with the resultthat an unduly high proportion of inadvertent breakages would result.

It is desirable that ampuls of the kind herein set forth should breakcleanly at the neck without splintering and withoutpresenting an undulyjagged edge at the break. Maintenance of the wall thickness at the neckas herein prescribed enhances the probability that the ampuls will breakcleanly as compared with ampuls having wall thicknesses at the neck lessthan herein prescribed.

The invention is especially applicable to ampuls which are drawn fromglass tube and when the ampuls are made in this way a sufficientthickness of the ampul Wall at the neck can be achieved by allowing theflame to play upon the neck for a sufficient length of time havingregard to the temperature of the flame. In the case of such ampuls it isdesirable that the glass tube from which they are made should be ofrelatively uniform thickness which does not vary, at least in thecircumferential direction and preferably also in the longitudinaldirection, by more than from a mean value i.e. by more than in all.

In the preferred form of ampul the neck is scored to form a short notchin the external surface thereof but alternatively ampuls may be scoredto form an arc or a ring in and extending around the external surfacethereof. The scoring should of course be performed at or very near tothe minimum circumference of the neck.

- Since it has been established that the ratio between the wallthickness at the constriction and the diameter of the constriction isimportant to minimize inadvertent breakage, likewise the length anddepth of the scratch or notch 5 should be kept as small as possibleconsistent with enabling the ampul to be conveniently broken at theconstriction. In most cases, and especially in the case of smalldiameter constrictions of the order of 4 to 5 millimetres the merestskin abrasion is sulficient. In the case of large ampuls of 10millimetres or more in neck diameter the depth of scoring should notexceed 25% of the thickness of the Wall at the neck of the ampul and inthe case of small ampuls having necks of the order of 4 miliimetres to 6millimetres in diameter the depth of scoring should be of the order of5% to 10% of the wall thickness at the neck. As a rule it is preferablethat the length of the scratch or notch should not be more than 20% ofthe length of the circumference where it is made.

The above ratios as to wall thickness and length and depth of notch havebeen given with direct reference to ampuls formed of neutral glass, andit will be understood that these dimensions may vary slightly withglasses of different kind. For example, with the tougher borosilicateglass the wall thickness at the constriction might be slightly less andthe lower limit of thickness may be 7% of the neck diameter, oralternately the depth or length of the notch might be slightly greater.For glass of less resistance to breakage than neutral glass the lowerlimit of wall thickness should be 9% of the neck diameter.

Inadvertent breakage is also lessened by annealing the ampul after thescratching or notching operation. Normally onewould think that the notchor groove or other weakening instrumentality might be applied at theapex of the constriction after annealing in order to set up apredetermined initial strain in such localized area, whereas annealingof the glass after the formation of the notch or groove obviously wouldtend to normalize the glass at this point. I have found, however, thatsatisfactory results are best obtained in getting maximum resistance toinadvertent breakage and giving sufiicient concentration of appliedforces to effect clean breakage by sort of balancing the breakageconstruction, namely the neck and the groove, against the normalizing orannealing of the glass after forming the constriction and the groove,bearing in mind, of course, the proper proportioning of the wallthicknesses and depth of the groove. It will thus be seen that I haveprovided an ampul of extremely inexpensive construction which offersmaximum resistance against inadvertent breakage and which adapts itselfto purposeful breakage by the correct application of finger pressure.

it is desirable to provide indicia at the notch or are or at a point inthe constriction diametrically opposite thereto and this may be done bythe application to the notch or arc or the diametric point, of asuitable colored fusible material 6 prior to annealing, such materialbeing fused into the glass as a result of the annealing; the subsequentannealing, as in the case of the formation of the notch, serving tomaintain the normalization of the glass and thus eliminate any strainsthat might be set up by the fusing operation. Although the coloredfusible material 6 is for the sake of clarity shown in Figure 3 at thatside of the neck opposite to the notch 5 it is preferred that thematerial 6 should be applied directly to the notch 5.

Said fusible material may have a coefficient of expan-'' the scoringitself as a thin narrow transverse band and 1 to engage lightly againstthe neck of the ampul to grind may be in the form of a suitable coloredglass paste.

The scoring may be performed by scratching, grinding of etching. Forexample a high speed rotary tool such as a steel'disc or a siliconcarbide wheel may be allowed a suitable scoring therein or alternativelythe scoring may be scratched in the neck of the ampul with a diamond oragain the scoring may be etched by the application of a paste containinga mordant such as ammonium. bifluoride.

When ampuls are scored to form an are or ring in and extending aroundthe external surface of the neck the colored fusible material may beapplied as a thin narrow band covering either a part or the whole of thescoring. Even when the scoring extends as a ring right around the ampulneck it is still desirable to apply a colored fusible material to theneck in order to indicate that the ampul is one which can be brokenWithout the aid of a file. When the scoring is formed as a short notchthe application of colored fusible material to the notch or arc will notonly indicate that the ampul is one that can be broken without the aidof a file but will also indicate the position at which the ampul can bebroken and the direction in which the bending moment should be applied.7

When the scoring is a short notch it is preferable that the coloredfusible material should be applied directly to the notch to indicate thedirection in which the bending moment should be applied but the coloringmaterial could be applied at some other part of the neck for example onthat side opposite to the notch. It is however desirable that all ampulsshould be similarly marked so as to build up amongst consumers a properunderstanding as to the correct mode of breakage.

In conjunction with the maintenance of the herein specified ratios ofwall thickness at the neck to external diameter at the neck the presentinvention includes other methods of preweakening ampuls such for exampleas by the application of a cold tool to the neck of the ampul when hotor by the application to the neck of a fusible material of coeflicientof expansion different to that of the material of which the ampul ismade whereby to set up an initial stress in the ampul to preweaken it.Even if such fusible material is of approximately the same coefiicientof expansion as the material of which the ampul is made it may by virtueof the locally increased thickness of the wall of the neck give rise toan abrupt change of neck strength and thereby preweaken the neck in sofar as the neck will break the more readily at the point where theabrupt change of strength occurs. It is believed however thatpreweakening of the neck by the application of a fusible material to theneck without scoring as herein described is not as satisfactory asscoring of the neck from the point of view of achieving a satisfactoryclean break and of avoiding inadvertent breakage.

In the application of the invention to ampuls which are drawn from glasstube which is rotated about its longitudinal axis whilst a flame isapplied thereto, a suflicient wall thickness at the neck as hereindescribed is achieved by allowing the flame to play upon the neck for asuflicient period of time with the result that the thickness of theglass wall at the neck will as a rule be considerably greater thanelsewhere in the ampul.

The amprul shown in the drawings is one which has been drawn from glasstube and it will be noted from Figure 2 that the wall thicknessdecreases away from the neck 1.

The invention includes ampuls made as described above and the preferredform of ampul has a wall thickness at the neck as herein prescribed andhas a short transverse notch or scratch scored in the external surfaceof the neck with a colored material fused to the neck at the notch orscratch.

Whilst most ampuls of the kind with which the present invention isconcerned are despatched by the ampul manufacturer in an open conditionto the manufacturer of the contents it is sometimes preferred that theampuls should be despatched to the manufacturer of the contents in aclosed condition, usually with an enlarged or bell shaped top, which issubsequently cut off by the manufacturer of the contents so that thecontents can be inserted into the ampul which is subsequentlyhermetically sealed at the place where the bell top was cut off. It isto be clearly understood that such ampuls are included within the scopeof the appended claims, wherein the words hermetically sealed are usedto indicate that the present invention is not concerned with glasscontainers which are adapted to be corked or closed otherwise than byhermetic sealing.

I claim:

1. A glass ampul comprising a tubular body having a constricted neckportion, means for preweakening said constricted portion generally inthe zone of lease diameter, the ratio of the thickness of the wall ofsaid constricted portion in said preweakened zone to the outsidediameter in said zone being not less than 8 to 10%, depending on theoutside diameter, said ratio being 8% for ampuls having an outsidediameter of about 10 millimeters or more in said zone and 10% for ampulshaving an outside diameter of about 4 millimeters in said zone, theratio being inversely proportional to the outside diameter of theconstricted portion in said zone, the thickness of the wall of saidconstricted portion increasing progressively toward and adjacent eachside of said means for preweakening, said means for preweakening beingsuflEicient to facilitate intentional breakage at said zone by theapplication of a bending moment thereto by the tingers and thumbs butinsufficient to cause inadvertent breakage during the normal handling incleaning, filling and transportation.

2. The ampul set forth in claim 1, in which said ratio is not more than15%.

3. The ampul set forth in claim 1, said means for preweakening saidconstricted portion comprising a transverse score mark.

4. The ampul set forth in claim 3 including colored material on saidampul to indicate the position of the score mark in said zone.

5. The ampul set forth in claim 3 wherein the depth of said score markis not more than 25% of the wall thickness at said zone.

References Cited in the file of this patent UNITED STATES PATENTS741,823 Packer Oct. 20, 1903 1,371,668 Davis Mar. 15, 1921 1,922,811Kabnick Aug. 15, 1933 1,951,743 Thomae Mar. 20, 1934 1,956,568 Fjord May1, 1934 2,371,486 Walker Mar. 13, 1945 2,486,321 OSullivan Oct. 25, 19492,517,604 Smith Aug. 8, 1950 FOREIGN PATENTS 8,936 Sweden Nov. 30, 1897572,176 Great Britain Sept. 26, 1945

